//
//  UIImage+UrlSize.m
//  NiuWaJiaoYu
//
//  Created by MinLison on 2018/1/9.
//  Copyright © 2018年 niuwaketang. All rights reserved.
//

#import "UIImage+UrlSize.h"

@implementation UIImage (UrlSize)
// 根据图片url获取图片尺寸
+(CGSize)getImageSizeWithURL:(id)imageURL
{
        NSURL* URL = nil;
        if([imageURL isKindOfClass:[NSURL class]]){
                URL = imageURL;
        }
        if([imageURL isKindOfClass:[NSString class]]){
                URL = [NSURL URLWithString:imageURL];
        }
        if(URL == nil)
                return CGSizeZero;                  // url不正确返回CGSizeZero
        
        NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:URL];
        NSString* pathExtendsion = [URL.pathExtension lowercaseString];
        
        CGSize size = CGSizeZero;
        if([pathExtendsion isEqualToString:@"png"]){
                size =  [self getPNGImageSizeWithRequest:request];
        }
        else if([pathExtendsion isEqual:@"gif"])
        {
                size =  [self getGIFImageSizeWithRequest:request];
        }
        else{
                size = [self getJPGImageSizeWithRequest:request];
        }
        if(CGSizeEqualToSize(CGSizeZero, size))                    // 如果获取文件头信息失败,发送异步请求请求原图
        {
                NSData* data = [NSURLConnection sendSynchronousRequest:[NSURLRequest requestWithURL:URL] returningResponse:nil error:nil];
                UIImage* image = [UIImage imageWithData:data];
                if(image)
                {
                        size = image.size;
                }
        }
        return size;
}
//  获取PNG图片的大小
+(CGSize)getPNGImageSizeWithRequest:(NSMutableURLRequest*)request
{
        [request setValue:@"bytes=16-23" forHTTPHeaderField:@"Range"];
        NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
        if(data.length == 8)
        {
                int w1 = 0, w2 = 0, w3 = 0, w4 = 0;
                [data getBytes:&w1 range:NSMakeRange(0, 1)];
                [data getBytes:&w2 range:NSMakeRange(1, 1)];
                [data getBytes:&w3 range:NSMakeRange(2, 1)];
                [data getBytes:&w4 range:NSMakeRange(3, 1)];
                int w = (w1 << 24) + (w2 << 16) + (w3 << 8) + w4;
                int h1 = 0, h2 = 0, h3 = 0, h4 = 0;
                [data getBytes:&h1 range:NSMakeRange(4, 1)];
                [data getBytes:&h2 range:NSMakeRange(5, 1)];
                [data getBytes:&h3 range:NSMakeRange(6, 1)];
                [data getBytes:&h4 range:NSMakeRange(7, 1)];
                int h = (h1 << 24) + (h2 << 16) + (h3 << 8) + h4;
                return CGSizeMake(w, h);
        }
        return CGSizeZero;
}
//  获取gif图片的大小
+(CGSize)getGIFImageSizeWithRequest:(NSMutableURLRequest*)request
{
        [request setValue:@"bytes=6-9" forHTTPHeaderField:@"Range"];
        NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
        if(data.length == 4)
        {
                short w1 = 0, w2 = 0;
                [data getBytes:&w1 range:NSMakeRange(0, 1)];
                [data getBytes:&w2 range:NSMakeRange(1, 1)];
                short w = w1 + (w2 << 8);
                short h1 = 0, h2 = 0;
                [data getBytes:&h1 range:NSMakeRange(2, 1)];
                [data getBytes:&h2 range:NSMakeRange(3, 1)];
                short h = h1 + (h2 << 8);
                return CGSizeMake(w, h);
        }
        return CGSizeZero;
}
//  获取jpg图片的大小
+(CGSize)getJPGImageSizeWithRequest:(NSMutableURLRequest*)request
{
        [request setValue:@"bytes=0-209" forHTTPHeaderField:@"Range"];
        NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
        
        if ([data length] <= 0x58) {
                return CGSizeZero;
        }
        
        if ([data length] < 210) {// 肯定只有一个DQT字段
                short w1 = 0, w2 = 0;
                [data getBytes:&w1 range:NSMakeRange(0x60, 0x1)];
                [data getBytes:&w2 range:NSMakeRange(0x61, 0x1)];
                short w = (w1 << 8) + w2;
                short h1 = 0, h2 = 0;
                [data getBytes:&h1 range:NSMakeRange(0x5e, 0x1)];
                [data getBytes:&h2 range:NSMakeRange(0x5f, 0x1)];
                short h = (h1 << 8) + h2;
                return CGSizeMake(w, h);
        } else {
                short word = 0x0;
                [data getBytes:&word range:NSMakeRange(0x15, 0x1)];
                if (word == 0xdb) {
                        [data getBytes:&word range:NSMakeRange(0x5a, 0x1)];
                        if (word == 0xdb) {// 两个DQT字段
                                short w1 = 0, w2 = 0;
                                [data getBytes:&w1 range:NSMakeRange(0xa5, 0x1)];
                                [data getBytes:&w2 range:NSMakeRange(0xa6, 0x1)];
                                short w = (w1 << 8) + w2;
                                short h1 = 0, h2 = 0;
                                [data getBytes:&h1 range:NSMakeRange(0xa3, 0x1)];
                                [data getBytes:&h2 range:NSMakeRange(0xa4, 0x1)];
                                short h = (h1 << 8) + h2;
                                return CGSizeMake(w, h);
                        } else {// 一个DQT字段
                                short w1 = 0, w2 = 0;
                                [data getBytes:&w1 range:NSMakeRange(0x60, 0x1)];
                                [data getBytes:&w2 range:NSMakeRange(0x61, 0x1)];
                                short w = (w1 << 8) + w2;
                                short h1 = 0, h2 = 0;
                                [data getBytes:&h1 range:NSMakeRange(0x5e, 0x1)];
                                [data getBytes:&h2 range:NSMakeRange(0x5f, 0x1)];
                                short h = (h1 << 8) + h2;
                                return CGSizeMake(w, h);
                        }
                } else {
                        return CGSizeZero;
                }
        }
}
@end
